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Papers by Rattaya Yalamanchili

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), 1997

Series on Advances in Mathematics for Applied Sciences, 1995

International Journal of Engineering Science, 1994

Electra-rheological materials are suspensions of particles in non-conducting fluids, and all mode... more Electra-rheological materials are suspensions of particles in non-conducting fluids, and all models that have been developed to date describe their behavior by treating them as a homogenized single continuum, and ignoring the multicomponent structure of the material. The theory of interacting continua is ideally suited for modeling such mixtures and in this paper we present a simple theory which takes into account the distribution of the particles in the fluid, the applied electric field, and the relative motion of the two constituents. To illustrate the utility of such a theory we study the flow of an electro-rheological material between two parallel plates under the application of an electrical field normal to the plates.

Particulate Science and Technology, 2000

... RAJAGOPAL KR (1) ; GUPTA G. (2) ; YALAMANCHILI RC (3) ; ... Here, we discuss the development ... more ... RAJAGOPAL KR (1) ; GUPTA G. (2) ; YALAMANCHILI RC (3) ; ... Here, we discuss the development of an instrument which can evaluate the material properties of grannular ... verify the commonly exhibited phenomena by these materials and estimate the various forces which are ...

International Journal of Non-Linear Mechanics, 1994

ABSTRACT

Journal of Non-Newtonian Fluid Mechanics, 1995

Measurements of the velocity using Laser Doppler Velocimetry and normal stress are made for the f... more Measurements of the velocity using Laser Doppler Velocimetry and normal stress are made for the flow of dilute polymer solutions through a channel with corrugated top and bottom plates. (Since we are dealing with non-Newtonian fluids, there can be significant contributions to the normal stress from non-linear terms in the constitutive expression, even when the flow is slow. The measurements being made are the normal stresses and not the “pressure”.) The surfaces of the plates are sinusoidal. A Reynolds number based on half the average plate spacing as the length scale and the characteristic velocity as the velocity scale was used and the range of Reynolds numbers studied was 50 < Re < 1000. The centerline velocities indicate that the experiments were performed in the inertial regime, as confirmed by the asymmetry of the centerline velocities along the channel length. The velocity profiles at the trough near the wall, for a channel with wavelength of 2.54 cm, indicate the presence of secondary flow. Sinusoidal plates with nearly identical aspect ratios (aλ) allowed for dramatic changes in the way in which the friction factor varied with Reynolds number, in that, in one case the friction factor associated with the fluid without polymer was higher than the friction factor associated with the fluid with polymer, while in others it was just the opposite. This would call into question the use of aspect ratio as an appropriate parameter for studying such problems. Changes in plate wavelength either increased or decreased the friction factor depending on the Reynolds number. Increasing plate amplitude increased the friction factor of the fluid for the range of values for the Reynolds number that was considered. The amplitude associated with the dimensionless normal stress increased with decreasing wavelength, for particular Reynolds numbers, irrespective of the fluid studied. Increasing the polymer concentration in the fluid decreased the difference in the amplitude of the dimensionless normal stress, the Reynolds number being fixed. Increasing the plate amplitude increased the amplitude of the normal stress, while an increase in plate wavelength decreased the amplitude of the normal stress.

International Journal of Non-Linear Mechanics, 1993

The centerline velocities and the velocity profiles were measured for fluids in a corrugated chan... more The centerline velocities and the velocity profiles were measured for fluids in a corrugated channel with the top and bottom plates sinusoidal with and without polymer additives, using laser Doppler velocimetry. It was observed that for the range of Reynolds number studied the velocity profiles and centerline velocities are qualitatively similar for the fluids with and without polymer additives. It was also observed that an increase in the aspect ratio (aλ;a = amplitude, λ. = wavelength) of the plates showed the presence of secondary flow in the channel for the fluids with and without polymers in them. However, the previous study (ef. Yalamanchili et al. [1]) clearly showed that the aspect ratio is not the appropriate non-dimensional number to be used in correlating normal stress data for non-Newtonian fluids. As expected, the velocity increased in the converging regions of the channel and decreased in the diverging regions of the channel, irrespective of the Reynolds number of the fluid flowing, the maximum and minimum velocity always occurred at the same location.